In U.S. Pat. No. 4,344,825 issued Aug. 17, 1982, to D. R. Colwell, there is described a distillation system wherein spent cleaning solvent, such as used to clean printed circuit boards, is reclaimed by passage through a pair of distillation chambers. The spent solvent distilland is initially distilled in a conventional distillation chamber and then metered amounts of residue slurry are advanced into a second chamber. In this second chamber each metered charge is deposited on a heated plate in front of one of an array of rotating blades. A blade engages and wipes each charge of slurry over the heated plate to vaporize entrapped solvent which rises and is condensed and returned to the first distillation chamber, whereafter the blade advances the remaining residue to a discharge conduit.
Many other distillation systems have been devised wherein distilland is flowed onto one or more heated plates over which the distilland is moved while being vaporized. U.S. Pat. No. 2,313,175 issued Mar. 9, 1943, to R. F. Scott et al. shows a vacuum chamber with a stack of spaced heating plates that are rotated to centrifugally move a distilland over the edge of an upper plate and onto successive lower plates in the stack. Portions of the distilland are vaporized by each heated plate to form rising vapors which are condensed and recovered. The residue distilland on the lowermost plate is exited from the distillation chamber.
In U.S. pat. No. 2,818,373 issued Dec. 31, 1957, to C. Ockrent, there is disclosed a vacuum distillation chamber having a single heated plate for receiving a distilland which is spread by a rotating scraper cooperating with the face of the plate to form vapors which rise and are condensed on the inside of the top surface of the chamber. Residue products are pushed to the edge of the plate and allowed to fall and drain from the chamber through an exit pipe at the bottom of the chamber.
There is still a need for a distillation system comprising a single distillation chamber wherein the distillation is accomplished at atmospheric pressure, and wherein discrete charges of distilland may be distilled in such a fashion that all of the distilland is recovered and the residue may be subsequently cyclically discharged in a condition that is substantially free of the distilland.